如何使用mgo（golang）创建哈希索引

huangapple
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英文:

How to create hashed index by mgo (golang)

问题

你可以使用mgo包来创建（或确保）哈希索引。以下是相当于你提供的代码的Go代码：

  1. index := mgo.Index{
  2.     Key:        []string{"hashed:_id"},
  3.     Background: true,
  4. }
  6. err := collection.EnsureIndex(index)
  7. if err != nil {
  8.     // 处理错误
  9. }

这段代码使用EnsureIndex方法来创建哈希索引。Key字段指定要创建索引的键，hashed:_id表示要对_id字段进行哈希索引。Background字段设置为true表示在后台创建索引。

请确保在使用此代码之前已经正确导入了mgo包，并且已经建立了与MongoDB的连接。

英文:

How can I create (or ensure) hashed index with mgo package?

I need a go code to be equivalent with this:

  1. >> db.collection.createIndex( { _id: "hashed" } )

I have tried using runCommand but there is only ‍createIndexes command that want a list of index specs. And I have no idea what is that and how I can create index specs.

答案1

得分: 3

你可以按照Collection.EnsureIndex中的文档进行操作：

> 通过该API还支持其他类型的索引。以下是一个示例：

  1. index := Index{
  2.     Key: []string{"$2d:loc"},
  3.     Bits: 26,
  4. }
  5. err := collection.EnsureIndex(index)

> 上面的示例请求创建了一个针对"loc"字段的"2d"索引。

所以基本上，你可以使用以下格式：$<indexType>:<indexedField>，如下所示：

  1. package main
  3. import mgo "gopkg.in/mgo.v2"
  5. const (
  6.     db   = "so_hashed_idx"
  7.     coll = "testcoll"
  8. )
  10. func main() {
  11.     var s *mgo.Session
  12.     var err error
  14.     if s, err = mgo.Dial("127.0.0.1:27017"); err != nil {
  15.         panic(err)
  16.     }
  18.     // 索引规范只是一个花哨的词，用于将键或键/值对传递给Index类型的Key切片。
  19.     idx := mgo.Index{
  20.         Key: []string{"$hashed:_id"},
  21.     }
  23.     if err := s.DB(db).C(coll).EnsureIndex(idx); err != nil {
  24.         panic(err)
  25.     }
  26. }

构建并运行上述代码将显示so_hashed_idx.testcoll的索引如下：

  1. > db.testcoll.getIndices()
  2. [
  3.     {
  4.         "v" : 1,
  5.         "key" : {
  6.             "_id" : 1
  7.         },
  8.         "name" : "_id_",
  9.         "ns" : "so_hashed_idx.testcoll"
  10.     },
  11.     {
  12.         "v" : 1,
  13.         "key" : {
  14.             "_id" : "hashed"
  15.         },
  16.         "name" : "_id_hashed",
  17.         "ns" : "so_hashed_idx.testcoll"
  18.     }
  19. ]
英文:

You can do it as documented at Collection.EnsureIndex:

> Other kinds of indexes are also supported through that API. Here is an example:

  1. index := Index{
  2.     Key: []string{"$2d:loc"},
  3.     Bits: 26,
  4. }
  5. err := collection.EnsureIndex(index)

> The example above requests the creation of a "2d" index for the "loc" field.

So basically, you have the format $<indexType>:<indexedField>, as shown below:

  1. package main
  3. import mgo "gopkg.in/mgo.v2"
  5. const (
  6. 	db   = "so_hashed_idx"
  7. 	coll = "testcoll"
  8. )
  10. func main() {
  11. 	var s *mgo.Session
  12. 	var err error
  14. 	if s, err = mgo.Dial("127.0.0.1:27017"); err != nil {
  15. 		panic(err)
  16. 	}
  18. 	// An index spec is nothing more than a fancy word for the keys
  19. 	// or the key/value pairs handed over to the Key slice of the
  20. 	// Index type.
  21. 	idx := mgo.Index{
  22. 		Key: []string{"$hashed:_id"},
  23. 	}
  25. 	if err := s.DB(db).C(coll).EnsureIndex(idx); err != nil {
  26. 		panic(err)
  27. 	}
  28. }

Building and running the above results in so_hashed_idx.testcoll showing its indices as follows

  1. > db.testcoll.getIndices()
  2. [
  3.     {
  4. 	    "v" : 1,
  5. 	    "key" : {
  6. 		    "_id" : 1
  7. 	    },
  8. 	    "name" : "_id_",
  9. 	    "ns" : "so_hashed_idx.testcoll"
  10.     },
  11.     {
  12. 	    "v" : 1,
  13. 	    "key" : {
  14. 		    "_id" : "hashed"
  15. 	    },
  16. 	    "name" : "_id_hashed",
  17. 	    "ns" : "so_hashed_idx.testcoll"
  18.     }
  19. ]

答案2

得分: 2

使用runCommand的答案：

  1. func createHashedIndex(session *mgo.Session, collectionName string, indexKey string) {
  2.     var result interface{}
  3.     if err := session.Run(bson.D{
  4.         {"runCommand", collectionName},
  5.         {"command", []bson.M{bson.M{"name": indexKey+"_hashed_index", "key": bson.M{indexKey: "hashed"}}}}}, &result); err != nil {
  6.         fmt.Println("创建索引错误：", err.Error())
  7.     } else {
  8.         fmt.Println("创建索引：", result)
  9.     }
  10. }
英文:

An answer with runCommand:

  1. func createHashedIndex(session *mgo.Session, collectionName string, indexKey string){
  2. 	var result interface{}
  3. 	if err := session.Run(bson.D{
  4. 		{"createIndexes", collectionName},
  5. 		{"indexes", []bson.M{bson.M{"name": indexKey+"_hashed_index", "key": bson.M{indexKey: "hashed"}}}}}, &result); err != nil {
  6. 		fmt.Println("Create Index Error:", err.Error())
  7. 	} else {
  8. 		fmt.Println("Create Index:", result)
  9. 	}
  10. }

huangapple
  • 本文由 发表于 2017年7月29日 20:41:17
  • 转载请务必保留本文链接：https://go.coder-hub.com/45389410.html
  • go
  • mgo
  • mongodb
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